I've been using Amazon Cloud now for a few months. I am using it strictly for backup purposes. I was using Amazon S3, but the unlimited space for $60 a year is about half I am paying for the S3 account.
The problem is that the interface is really terrible. You can login using existing Amazon un/pw, which is great. You can go to amazon.com/clouddrive and start dragging and dropping files, which is also great. You can also install the desktop app, but if you upload file using that, it puts the files in the rooter directory. I can't figure out a way to put files in specific locations using the desktop app. You can go back and move them at amazon.com/clouddrive, but web interface is really bad.
It's all because the web interface is so unresponsive at times. You click on a directory and you wait a few seconds for it to go to that location, or if you create a folder, you wait. Yes, it's only seconds, but those seconds add up.
Sometimes if I am uploading a lot of files, it will become completely unresponsive. I will click on a directory that I know has files in it, and it shows nothing. Sometimes I can refresh the page and they show up, but other times I just can't get it to load the files. Because of all of this, it is taking me weeks to get on my files up there. Yes, I have a TB+ worth of files, but the pitch is "unlimited".
I want to use this to backup my ext hard drive, and do this frequently to back up new and new versions of files. I use "Beyond Compare" to sync my hard drive with another back up HD, but now I want this same functionality in the cloud, so that's why I went to Amazon Cloud.
I am using NetDrive to load my Amazon Cloud account as a drive on my PC, and then I use Beyond Compare to compare my HD with my Amazon Cloud drive. This works, in theory, but NetDrive will always disconnect with Amazon after a while. I would say this is a NetDrive issue, but my experience with Amazon Cloud tells me that it is the weak link.
Once I have everything backed up I will reevaluate. I have well over a TB to get up there, and I'm only half way. It's a long process. I wish I could just get it all uploading and wake up the next day with it done, but that doesn't seem to be an option.